The present invention relates to an autonomous hydraulic expansion and contraction apparatus, and more particularly to an autonomous hydraulic expansion and contraction apparatus configured such that the expansion and contraction length of a support unit is expanded and contracted to the coupling length of the expansion and contraction equipment by simple manipulation of a valve unit and such that oil replenishment is rapidly achieved.
In general, a turnbuckle is typically used as an apparatus for expanding and contracting shafts of various kinds of machines and an apparatus for controlling the tensile force of construction equipment.
The turnbuckle is an apparatus for pulling and tightening a rope, a chain, a wire, etc. The turnbuckle is provided at the left and right sides thereof with screw bars. One of the male screws is a right-handed screw, and the other of the male screws is a left-handed screw. When members haying female screws, such as nuts, are rotated in one direction, the two male screws approach each other. When the nuts are rotated in the opposite direction, the two male screws are moved away from each other.
When a support bar, a support steel rope, a steel bar, a rope, etc. of a structure is tightly pulled using the above operating process, the turnbuckle is disposed in the middle of it such that the turnbuckle is rotated to tightly pull it, thereby controlling the tensile force of it.
The structure of a turnbuckle, which is a typical example of the above expansion and contraction apparatus, will be described with reference to FIGS. 1 and 2.
In a turnbuckle, which is configured to achieve axial connection such that a coupling length is adjustable between opposite coaxial rod members that are expansible and contractible, female parts 11 and 12, to which male type rod members 21 and 22 are coupled, are formed in the ends of a female type tubular sleeve 10, one of the ends of the sleeve and a corresponding one of the rods coupled thereto are provided with left-handed screws, and the other of the ends of the sleeve and another corresponding one of the rods coupled thereto are provided with right-handed screws.
When the sleeve 10 is rotated, the rods 21 and 22 are introduced into the sleeve 10 or are withdrawn from the sleeve 10 depending on the direction in which the sleeve 10 is rotated. After a required axial distance is achieved between the two rods 21 and 22, the turnbuckle is fastened using a fastening member.
The turnbuckle is formed by casting or forging. When a support bar, a support steel rope, a steel bar, a rope, etc. of a structure is tightly pulled, the turnbuckle is disposed in the middle of it such that the turnbuckle is rotated to tightly pull it.
In the turnbuckle, which is generated used as the expansion and contraction apparatus, as described above, screws having corresponding directions are formed in the ends of the opposite coaxial rods and the inside of the sleeve such that the corresponding screws interact with each other via the rotation of the sleeve to adjust the coupling length therebetween. In order to adjust the length, it is necessary to continuously rotate the sleeve, to which the screws are coupled, with the result that much time and cost are needed.
In addition, in the conventional turnbuckle, the coaxial rods, which have screws corresponding to the screws formed in the sleeve, are screw-coupled to the sleeve such that coupling length is adjusted by the rotation of the sleeve. Since the length is adjusted by the movement of the coaxial rods in response to the rotation of the screws, a backlash phenomenon occurs due to the gap in the coupling space between the screw threads. As a result, the expansion and contraction length is changed by a predetermined distance depending on variation in displacement after the adjustment of the length.
Furthermore, in the conventional turnbuckle, when the turnbuckle is moved in the state in which the opposite coaxial rods are screw-coupled to the middle sleeve so as to adjust the length, the coupled screws are rotated and unfastened, with the result that it is not possible to maintain the expansion and contraction length uniform.
In addition, the conventional turnbuckle is configured to be expansible when the turnbuckle is rotated in one direction and to be contractible when the turnbuckle is rotated in the opposite direction since the screws formed in corresponding directions are coupled to each other. Consequently, the expansion and contraction strength that the screw threads can withstand is limited, whereby it is difficult to use a turnbuckle using screws if more than a predetermined capacity is required.